In the PROFINET world, PROFINET Real-Time (RT) and PROFINET Isochronous Real-Time (IRT) are common terms. But, what is the difference between PROFINET RT and IRT? This video makes a detailed comparison that includes mechanisms, applications, implementation options, such as cabling, switches, topologies, and more.
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PROFINET RT vs IRT
PROFINET is a communication protocol to exchange data between controllers and devices. PROFINET can operate in demanding industrial environments and can deliver the speed and precision required by manufacturing plants. To ensure appropriate performance, PROFINET delivers data through the following communication channels:
1. TCP/IP (or UDP/IP)
2. PROFINET Real-Time (RT)
3. PROFINET Isochronous Real-Time (IRT)
4. Time Sensitive Networking (TSN)
PROFINET employs TCP/IP (or UDP/IP) communications for specific non-time-critical tasks, such as configuration, parameterization, and diagnostics.
PROFINET RT handles time-critical data exchange. An arriving PROFINET RT Ethernet frame has the PROFINET EtherType: 0×8892. Upon arrival at the destination node, the frame is directed straight from Ethernet (Layer 2) to the PROFINET application (Layer 7). The frame skips the TCP/IP layers and avoids the variable time it takes to be processed. Thus, communication speed and determinism improve significantly.
PROFINET RT meets the vast majority of the industry’s timing requirements, and almost all PROFINET frames are sent via this method. The overall performance will depend on network design, but generally, cycle times of 512 ms down to 250 µs can be achieved.
PROFINET IRT is a step beyond PROFINET RT.
Unavoidably, under high network traffic, some time-critical messages can gain jitter. PROFINET IRT eliminates variable data delays by enhancing the rules employed to switch Ethernet traffic and creating special rules for PROFINET traffic. It fulfills all synchronization requirements and allows deterministic communication with cycle times down to 31.25 µs and one µs of jitter.
Most PROFINET networks can solely rely on PROFINET RT for all cyclic data exchange. PROFINET IRT is optional and only required in specific high-performance applications.
PROFINET IRT is often used in the following applications:
- Packing machines
- Printing presses
- Plastic injection molding machines
- Wood-processing machines
- Glass-processing machines
- Ceramic-processing machines